The present invention relates to turbochargers for internal combustion engines, and, more particularly to apparatus and methods for controlling the performance of the turbine of a turbocharger.
The amount of combustion air that can be delivered to the intake manifold of an internal combustion engine, for combustion in the engine cylinders, is a limiting factor in the performance of the engine. Atmospheric pressure is often inadequate to supply the required amount of air for proper and efficient operation of an engine.
Therefore, it is known to equip an internal combustion engine with one or more turbochargers for compressing air to be supplied to one or more combustion chambers within corresponding combustion cylinders. The turbocharger supplies combustion air at a higher pressure and higher density than existing atmospheric pressure and ambient density. The use of a turbocharger can compensate for lack of power due to altitude, or to increase the power that can be obtained from an engine of a given displacement, thereby reducing the cost, weight and size of an engine required for a given power output.
Each turbocharger typically includes a turbine driven by exhaust gases from the engine, and one or more compressors driven by the turbine through a turbocharger shaft common to both the turbine and the compressor or compressors. The common shaft interconnects the turbine wheel of the turbine with the compressor wheel or wheels in the compressor section. A stream of exhaust gases from the engine is conducted from the exhaust manifold to the turbine. The stream of exhaust gases passing through the turbine causes the turbine wheel to rotate, thereby turning the common shaft interconnecting the turbine wheel and the compressor wheels and rotating the compressor wheels. The compressor receives the fluid to be compressed, which may be combustion air only or a mixture of combustion air and fuel, and supplies compressed fluid to the intake manifold of the engine.
It is known to condition the boost air flowing from the compressor or compressors, to affect the overall turbocharger performance, and or the engine efficiency. In turbochargers having multi-stage compressors, compressing the air in the first compressor significantly raises the temperature of the air, increasing the power required by the second compressor to achieve a desired pressure boost. To overcome the detrimental effects of the increase in temperature, so-called xe2x80x9cintercoolersxe2x80x9d have been provided in the flow path between the first compressor outlet and the second compressor inlet. Similarly, so-called xe2x80x9caftercoolersxe2x80x9d have been used after the turbocharger in turbochargers having both single-stage and multi-stage compressors. The aftercooler cools the compressed air supplied to the intake manifold, thereby increasing the oxygen content per unit volume to better support combustion in the cylinders, and decrease engine operating temperatures.
On the turbine side, it has been known to control exhaust flow to and from the turbine, using controllable vanes, to thereby affect overall turbocharger performance. Nozzles in both the inlet throat and the nozzle exit have been used. However, the controllable vane structures are expensive, and, as somewhat complex mechanical devices, can experience mechanical failures.
Under certain engine operating condition changes, turbocharger response can be slow in achieving the desired corresponding change in turbocharger performance. Desirably, the turbocharger will provide the required level of pressure boost, respond quickly to load changes, and function efficiently under both high load and low load conditions. This can be difficult to achieve efficiently, especially for an engine having a wide range of operating loads. If sized for full load conditions, the turbocharger responds slowly and provides minimal boost under low load conditions. Alternatively, improved response and boost under low load conditions can be achieved by providing a turbocharger that exceeds high load requirements, and using a waste gate to bypass excess exhaust flow when desired performance is reached. However, energy in the bypassed gas stream is wasted, and engine back-pressure is increased.
U.S. Pat. No. 4,769,993 discloses a turbocharger for internal combustion engines that includes a motor/generator integral with the compressor and turbine. In response to engine operating conditions, the motor/generator can be operated as a generator, supplying electric current to electrical storage batteries, and electrical systems of the engine or implement in which the engine is used. Under other operating conditions, the motor/generator can be operated as a motor, supplying torque to the turbine shaft to increase turbocharger performance.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect thereof, the invention provides an internal combustion engine with a plurality of combustion cylinders; an exhaust manifold coupled with at least some cylinders of the plurality of combustion cylinders; and an intake manifold coupled with the plurality of combustion cylinders. A turbocharger includes a turbine having a turbine inlet coupled with the exhaust manifold and a turbine outlet. A compressor has a compressor inlet and a compressor outlet. The compressor outlet is coupled with the intake manifold. A preheater is associated with the turbine inlet.
In another aspect thereof, the invention provides a turbocharger system with a turbine shaft; a turbine having a turbine casing defining a turbine inlet and a turbine outlet, and a turbine wheel mounted on the shaft and operatively disposed in the turbine casing; and a compressor having a compressor casing defining a compressor inlet and a compressor outlet, and a compressor wheel mounted on the shaft and operatively disposed in the compressor casing. A preheater is associated with the turbine inlet.
In yet another aspect thereof, the invention provides a method for turbocharging an internal combustion engine, having a plurality of combustion cylinders, an exhaust manifold and an intake manifold. The method includes steps of transporting exhaust gas from the combustion cylinders to the exhaust manifold; providing a turbocharger including a turbine having a turbine inlet and a turbine outlet, and a compressor having a compressor inlet and a compressor outlet; providing a preheater associated with the turbine inlet; driving the turbine with exhaust gas introduced at the turbine inlet; introducing combustion gas at the compressor inlet; transporting combustion gas from the compressor outlet to the intake manifold; and heating exhaust gas introduced at the turbine inlet.
In still another aspect thereof, the invention provides a method for operating a turbocharger, including steps of providing a turbocharger including a turbine having a turbine inlet and a turbine outlet, and a compressor having a compressor inlet and a compressor outlet; providing a fluid stream to the turbine inlet; driving the turbine with the fluid stream introduced at the turbine inlet; and heating the fluid stream entering the turbine inlet.